Research On Stability And Seismic Performance Of Asymmetric Spatial And Special-shaped Arch And Girder Composite Bridge

With the continuous development of the bridge industry,special-shaped arch bridges have developed rapidly due to their unique and novel structure.Driven by the development of bridge aesthetics,a large number of special-shaped arch bridges of various forms have emerged.The research object of this paper is an asymmetrical spatial profiled arch-girder composite bridge.The bridge is located on the "S" curve and is designed as a broken line with the concept of " use polylines instead of curves ".This paper uses the bridge as a basis to establish a spatial finite element model based on The static analysis studies the influence of various loads on the static characteristics of the bridge,and further studies the stability,dynamic characteristics and seismic performance.The analysis summarizes the three factors of the angle of flexure,the position of the angle,and the diameter of the cable.The influence law of dynamic characteristics.Through the research in this paper,we have learned about the mechanical properties of the bridge and its changing laws,which not only provides reference for the design of similar bridges,but also has guiding significance for the construction of the bridge.The main conclusions of this paper are as follows:(1)The bridge has a good structural force in the completed state and in use stage,and meets the requirements of the specification.The bridge has good stability in the no-stay phase and in the completed state of the bridge,and the temperature rise and the installation of the cables are not conducive to the stability of the bridge.The fundamental frequency of the special-shaped arch bridge is 1.400026 Hz,and the basic period is 0.714272 s.The first-order mode is that the longitudinal drift of the main girder of the full bridge is accompanied by vertical bending of the main girder of the connecting span,and the outer sides of the double-supported arch ribs of the large arch tower are horizontally bent out of plane.The bottom end of the special-shaped arch tower column and the tension arch rib of the bridge are weak parts of the force,and the design should be strengthened.(2)Comparing the static analysis results of the bridge under various load combinations shows that the live load will produce a greater response during the use phase of the bridge,which will greatly increase the stress of the whole bridge;the settlement of the support has an effect on the stress of the whole bridge.The effect of wind load is very small;wind load only has a greater impact on the stress of the special-shaped arch tower,and has little effect on the stress of the main girder and cable;the overall heating and overall cooling have a greater impact on the stress of the arch and the cable,and have a greater impact on the same The influence of the position or the stress of the same cable is opposite,that is,if the temperature increases,the stress increases,and the temperature decreases to decrease it.The live load greatly increases the vertical displacement of the full bridge,and has a significant impact on the lateral displacement of the special-shaped arch tower,and has a greater impact on the small arch tower;the settlement of the support has a greater impact on the vertical displacement of the full bridge;the lateral wind load has a greater impact on the bridge The lateral and vertical displacements have a great influence on the longitudinal displacement;the overall temperature change has a great influence on the displacement value and distribution law of the whole bridge in all directions;the maximum longitudinal displacement occurs in the tower columns of the two arch towers At the top,the two arch towers have a tendency to deform towards each other;under various load combinations,the vertical displacement distribution of the whole bridge is the same,and the maximum deflection occurs in the middle of the main arch ribs of the two special-shaped arch towers and the corresponding main beams.(3)The buckling mode and natural vibration mode analysis results show that the stiffness of the large arch tower of the bridge is less than that of the small arch tower,and the out-of-plane stiffness of the arch rib is less than the in-plane stiffness.In the bridge design,attention should be paid to the design of the large arch tower,Strengthen the design of structural stiffness outside the plane to enhance the economy of bridge design.The model parameters were changed for buckling analysis and natural vibration analysis.The results showed that with the increase of the cable diameter and the decrease of the connecting span angle,the natural vibration period increases and the stability coefficient decreases,which is beneficial to the seismic resistance of the bridge but not conducive to structural stability;Changes in cable diameter and connecting span’s bending angle have a greater impact on the stability and natural vibration characteristics of the lower-order characteristics,less on the higher-order characteristics,and little influence on the modal characteristics;the position of the connecting span’s inflection angle There is almost no effect on the stability and natural vibration characteristics of the bridge.(4)The seismic response spectrum analysis results show that the bridge has a tighter displacement coupling under the two working conditions of longitudinal seismic action on the large arch tower and vertical seismic action on the small arch tower.The combination of three-dimensional seismic action I affects the large arch tower and the small arch tower.There is a coupling effect between the arch tower,pile platform and combination II on the displacement response of the main girder.Under other conditions,the displacement response in the same direction as the seismic action(the seismic action with a combination coefficient of 1 in 3D seismic)is much larger than that in other directions;Compared with the seismic response,the E2 seismic response distribution law has not changed significantly,but the response value has increased significantly;the maximum seismic response may occur under both one-dimensional and three-dimensional seismic actions.Therefore,when studying the bridge seismic response,both one-dimensional and three-dimensional earthquake effect.